1. Field of the Invention
The present disclosure relates generally to a system and method for the efficient cultivation of algae in systems using in part or in full bioreactor chambers and other units wherein algae are grown in the presence of light and are then harvested for various uses including, but not limited to, for producing specific molecules, including recombinant molecules and other molecules produced from algae especially adapted to produce such molecules (including, but not limited to, nutracenticals and industrial polymers and polymer subunits), as food products and components of food products, and as biofuel or components of biofuel. Further wherein the pH of the algae slurry is manipulated to allow for automated removal of algae adhered to the light permeable surfaces of the bioreactor.
2. Background Art
Due to forces such as climate change, the instability of petroleum prices, and technological advancements, biofuels are being considered as a viable energy alternative. Biofuels made from food sources have proven controversial due to the fluctuating costs of feedstock, the adverse environmental impact presented by those feedstocks, and their effect on food prices and world hunger. It has become clear, therefore, that biofuels made from food crops will not provide the solution to the world's fuel or power generation challenges.
Research and development activities conducted on behalf of government and private industry have resulted in methods to generate biofuels from microscopic algae and similar and/or related microorganisms, which is particularly rich in oils that can be converted into biofuel. Microscopic algae have a yield per acre that is considerably higher than that of any other feedstock and its growth cycles are much shorter than other crops. Further, algae biofuels are biodegradable and are therefore relatively harmless to the environment if spilled.
At the industrial level, bioreactors that use microalgae and/or similar and/or related microorganisms to trap carbon dioxide and mono-nitrogen oxides are in active development in the United States, though the eventual commercial viability of these bioreactors remains in doubt. The success of such ventures will depend on the ability to mass produce algae by maximizing growth cycles and reducing factors that can contribute to the destruction or mutation of the algae in such a way as to diminish its viability or usefulness as a biofuel. Therefore, the development of a bioreactor that is able to efficiently grow and harvest microalgae at a low overall cost is necessary to realize the full potential of biofuels as a viable energy source.
Additionally, algae and/or other similar and/or related microorganisms may be used to produce a number of different products, including but not limited to, specific molecules, including recombinant molecules and other molecules produced from such microorganisms that especially adapted to produce such molecules (including, but not limited to nutraceuticals and industrial polymers and polymer subunits), as food products, and as components of food products.
However, prior to the present invention, it has been difficult to produce algae in quantities sufficient to meet industrial scale demands. For example, existing technologies for growing algae, for example for use as or in biofuels, can involve “open” or “partially-open” systems wherein algae are grown at least in part in open ponds. However, because light only penetrates to a slight depth in water, such systems produce a low amount of algae per land unit and water volume. There are also problems with evaporation of water, contamination of the algae stock, and unwanted (even potentially dangerous) access of animals (e.g., birds) to the algae as well as other undesirable aspects.
One means to circumvent these problems has been the attempted creation of efficient “closed” or “partially closed” bioreactors. In non-limiting examples, in “closed” bioreactors, an algae and water slurry are typically closed off from access to the outside environment (except, for example, for release of oxygen and other gases created by the growing algae and for the addition of nutrients and other materials to the solution to aid the growth of the algae) for the duration of the growth mode (i.e., prior to harvesting the algae). In “partially closed” bioreactors, part of the growth phase of algae may be in a closed system and part may be in an open system, such as a pond. For example, a closed bioreactor may be used to create a concentrated “seed” slurry of a desired algae which when at a sufficient density is then added to open ponds for further growth prior to harvesting. Such systems may help address issues such as unwanted overgrowth of non-preferred microorganisms in the open ponds due to the high initial seed concentration of the desired microorganism. Advantages of closed over open systems include the ability to potentially control access of the environment to the algae, and vice versa (thereby to, for example, avoid contamination of the algae or unwanted exposure of the algae to the environment and vice versa), to provide tighter controls over optimal conditions for algae growth, to increase the amount of algae produced per land unit and water volume, and to decrease evaporation of water.
Closed bioreactors may contain one or more light permeable “bioreactor” or similar units, regions, or the like, in which algae are exposed to light to induce them to undergo photosynthesis and reproduce. In some such instances, algae slurries may pass through such bioreactors, sometimes repeatedly, thereby maximizing exposure of the algae to light. Also, the algae slurry may be more tightly controlled (than, for example, in a pond of an open system) regarding, for example, nutrient content, pH, and temperature.
However, prior to the present invention, the production of Commercially important amounts of algae using any systems (closed, partially closed, open, and partially open) was limited due to a number of reasons. Some, as discussed, above, relate to open systems. Further, in closed systems problems have been encountered with, for example, algae and other similar microorganisms adhering to surfaces of the units, especially to the light permeable surfaces of bioreactors. This has proven to be a serious problem with the use of closed and partially closed bioreactors to grow algae in commercial quantities. The present invention overcomes these problems enhancing the production of algae and similar and/or related microorganisms for use in commercial applications such as biofuels.